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// Copyright (C) 2018 - IIT Bombay - FOSSEE
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
// Author:Sonu Sharma, RGIT Mumbai
// Organization: FOSSEE, IIT Bombay
// Email: toolbox@scilab.in
function [z, p, g] = cheb2ap (n, Rs)
//This function produces a lowpass analog Chebyshev type II prototype filter.
//Calling Sequence
//[z, p, g] = cheb2ap (n, Rs)
//Parameters
//n: Filter Order
//Rs: Stopband attenuation (in dB)
//z: Zeros
//p: Poles
//g: Gain
//Description
//This function designs a lowpass analog Chebyshev type II filter of nth order and with a stopband attenuation of Rs.
//Examples
//[z, p, g] = cheb2ap (4, 10)
//Output :
// g =
//
// 0.3162278
// p =
//
// - 0.1674887 + 0.9498949i
// - 1.1818323 + 1.1499912i
// - 1.1818323 - 1.1499912i
// - 0.1674887 - 0.9498949i
// z =
//
// - 1.0823922i
// - 2.6131259i
// 2.6131259i
// 1.0823922i
funcprot(0);
lhs = argn(1)
rhs = argn(2)
if (rhs < 2 | rhs > 2)
error("cheb2ap: Wrong number of input arguments.")
end
Rsf = 10 ^ (-Rs/20); //stop band pick to pick ripple in fraction
rs = Rsf ; //analpf function compitable stop band ripple (delta-s)
[hs,p,z,g]=analpf(n,"cheb2",[0 rs],1); //cutoff frequency of 1 rad/sec for prototype filter
p = p' ;
z = z' ;
g = abs(g);
endfunction
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